The present invention relates to the migration of the session information retained by a communication server.
In the mobile communication network, the widespread use of 4G LTE (Long Term Evolution) and WiMAX2+ (Worldwide Interoperability for Microwave Access) have enabled the use of high speed mobile broadband. Furthermore, with the availability of service such as LTE-Advanced, an expansion of the wireless band by carrier aggregation is enabling even faster mobile wireless communications.
The services utilizing LTE, in addition to internet access services, include VoLTE (Voice over LTE) service. With VoLTE service, a voice service utilizing a line switching service is realized by IP packet communications.
Now that the mobile communication network plays a significant role in the social infrastructure, failure prevention, swift recovery of network service during system failures, and service continuity are becoming prerequisite.
Now, the functions of the network nodes that used to require an exclusive apparatus are being realized by universal servers, such as those used in a data center, while NFV (Network Function Virtualization) which is operable at the virtual servers, configured virtually over the universal servers, has been studied. In the description below, universal servers configured to realize the features of the network nodes and the virtual servers realized over the universal server will be referred to as a communication server.
The system using the NFV is expected to increase the facility (scale out), decrease the facility (scale in) in accordance with the network load, change the system configuration due to migration of virtual servers for load distribution purposes, shorten a service down time which may occur during a system failure in a redundant system, and reduce an amount time needed for an effect to be apparent.
In response to the above stated expectations, a technology disclosed in a Japanese Unexamined Patent Application Publication No. 2012-103879 has been well known in the art. Japanese Unexamined Patent Application Publication No. 2012-103879 discloses “a session management method for a system having a plurality of server apparatus having a request allocation unit for returning a processing result of a client request to a client, a request processing unit for processing the received request, and a session information management unit for managing session information of the request, wherein the session information management unit of a first server apparatus moves information to the session information management unit of a second server apparatus, and the request allocation unit of the first server apparatus allocates the newly received request to the second server apparatus based on migration destination information of the moved session information in a case a migration time of the session information is later than a request received time when the request allocation unit of the first server apparatus receives a request and a response reply time when a processing result is replied to the client.”